Leprae

Morbus Hansen — Chronic infectious disease affecting skin, peripheral nerves, mucosa of the upper respiratory tract, and sometimes the eyes.

Aetiology

• Causative organism: Mycobacterium leprae
• Acid-fast bacillus, obligate intracellular pathogen
• Prefers cooler body areas (skin, peripheral nerves, nasal mucosa)

• Long incubation period: ~2–7 years (can be up to 20 years)

• Prolonged close contact with untreated cases

• Nasal droplets (most accepted route)

• Rare: broken skin contact, zoonotic transmission (armadillos in Americas)

Pathophysiology

• M. leprae invades Schwann cells → demyelination of peripheral nerves

• Immune response determines disease spectrum:
• Strong cell-mediated immunity → Tuberculoid (Paucibacillary)
• Weak cell-mediated immunity → Lepromatous (Multibacillary)

• Granuloma formation & nerve damage → sensory loss & deformities

Classification

WHO Clinical Classification

Ridley–Jopling Classification

1. Tuberculoid (TT) – PB, few lesions, strong immunity

2. Borderline Tuberculoid (BT)

3. Borderline Borderline (BB)

4. Borderline Lepromatous (BL)

5. Lepromatous (LL) – MB, many lesions, weak immunity

Clinical presentation

General Signs - 5A

• Achromia — Hypopigmented or erythematous patches

• Alopecia — Hair loss over lesions

• Anesthesia — Sensory loss (pain/temp/touch)

• Anhidrosis — Loss of sweating

• Athrophy

• Peripheral nerve thickening

Tuberculoid Leprosy

• Few well-defined patches

• Asymmetric lesions

• Early sensory loss prominent

• Nerve involvement localized

Lepromatous Leprosy

• Numerous symmetric skin lesions

• Nodules, diffuse infiltrations

• "Lion-like face" (leonine facies)

• Nasal crusting & destruction

• Symmetric peripheral neuropathy

• Eyebrow loss (madarosis)

Investigations

• Slit skin smear → Acid-fast bacilli (AFB) using Ziehl-Neelsen/Fite-Faraco stain

• Skin biopsy → granulomas, bacterial load assessment

• Lepromin test:
• Positive in tuberculoid
• Negative in lepromatous

Management

Paucibacillary (PB) — 6 Months

• Rifampicin 300 mg 2x1 monthly + Dapsone 100 mg 1x1 daily

Multibacillary (MB) — 12 Months

• Dapsone 100 mg 1x1 daily

• Rifampicin 300 mg 2x1 monthly

• Lamprene/Clofazimine 100 mg 3x1 monthly + 50 mg 1x1 daily

Investigations

• Peripheral neuropathy → deformities

• Claw hand, foot drop

• Corneal ulcer → blindness

• Nasal collapse

• Secondary infections, ulceration

Reactional States